Sound absorbing unit



Oct. 11, 1938. R. v. PARSONS f 2,132,642

SOUND ABSORBING UNIT Filed July 2l, 1932 v YAYAYAVAYAT'AYA l INVENTOR R gym om] FParJ/vs,

RNEY

Patentd t.11,193s l Y 2,132,642

N UNITED STATES PATsNT oFFloi:

SOUND ABSORBING UNIT Raymond V. Parsons, New York, N. Y.. assignor to Jolins-Manville Corporation, New York, N. Y., a corporation of New York y Application July 21, 1932, Serial N0. 623,799

4 Claims. (CL 154-45) This invention relates to a-sound dissipating forated in a manner adapted to admit incident and sound absorbing unit and particularly to one sound, as at positions 3 and 4. I have used to provided with a labyrinth of intercommunicating advantage perforations that range in diameter spaces between materials that may be relativelyfx from 0.03 to 0.06 inch, spaced on 1A inch centers.

5 ineffective per se in absorbing sound. A perforation of such size transmits sound with- 6 A preferred embodiment of the invention comout absorbing a large part thereof. When it is prises composited, spaced sheets of asbestos paper desired to decorate the outer sheet on the face oi or the like that are discontinuously perforated. the unit that is to be exposed to incident sound, The spaces may be constricted `at intervals with as by-painting or lacquering, the .perforations 4.

barriers or other means for deecting sound and in the outer sheet, may be somewhat larger, say, l0 causing it to pass, in part, from a given" space 0.2 inch in diameter, in order to avoid bridging through 'perforations into an adjacent space. over andvclosing of the holes by the decorating It is conventional to absorb sound in capillary material. or other small spaces in felts and similar mate- For best results, the perforations in the several A rials. Also, there are acoustical constructions in layers should be discontinuous, that is, the per- 15 which a felted sheet is provided with perforations forations in one layer do not register with those adapted to permit the entrance of sound into the in an adjacent layer. When the perforations are perforations and, through the side walls of pernonfregistering, sound passing through the perforations, into the multiplicity of small spaces beforations is largely reflected into the spaces 5 tween the individual fibers composing the sheet. which are defined by adjacent layers of sheet 20 In such constructions, the perforations are relamaterial and which extend laterally, in a directively large, whereas the spaces between the fibers tion that may be approximately parallel to the are smaller, in fact .very much smaller in area of face of the unit. cross section than the perforations. The spaces may be provided with constrictions,

The present invention provides a novel type of such as barriers or other means for deflecting the 25 acoustical unit in which perforations communisound at intervals and causing it to pass, in` part, cate with laterally extending passages that may through perforations communicating with an ad- ,be much larger than the perforations. Also, the l jacent space. The barriers or constrictions may linvention provides a. preformed sound absorbing take the form of cross-indentations or depreslight in weight, effective in thermal insulation, tend in a direction more or less at a right angle and adapted to bev decorated without the necesto the length of the corrugations.4 Preferably, sity of applying an independent facing member the cross-indentations do not close the space over the exposed surface. Other objects and adentirely.

3.3 vantages of the invention will appear as the de- In the structures of Figs. 1-3, the spacing 35 scription thereof progresses. means which maintain the spaced relationship y The invention is illustrated in the drawing in between adjacent layers of sheet material are the which corrugations of alternate sheets.

Fig. 1 is a perspective view, broken away in As an alternativev for the corrugations, there 4o part for clearness of illustration, of a preferred may be used other Spacing means, as, v101 example. 40

form of sound absorbing unit. indentations or irregularities of surface other Fig. 2 is a cross section taken on the line 2-2 of than corrugations. Also, theremay be used spac- Fig. 1. ing means' of the type illustrated in Fig. 4, which Fig. 3 is a cross section taken on the line 3-3 of shows sheets maintained in spaced relationship u .unit or block that is inexpensive to manufacture, sions 6 in the corrugated sheet. These may ex- 30 Fig. 1. to each other by means of spacing elements com- 45 Fig. 4 shows a modification of the invention Drising solid particles 8. These particles may comprising sheets of asbestos paper or the like consist of spongacork, or the like, suitably emand means for spacing the sheets from each bedded in the various sheets of material, as illusother. trated. In the various figures like reference characters V When spacing means such as illustrated in Fig. 50 denote like parts. i Y 4 are used, there are provided irregular spaces 9 Figures 1-3 show a sound absorbing vunit combetween the several layers of material in the unit.` prising a plurality of alternate layers ,of sheet It will be seen that the structure comprises a material i of plane surface composited with corsound-permeable facing sheet and a sheet memrugated sheets 2. The several layers are perber of uneven surface, as for example the corruierred at this time is asbestos paper. Other sheet material may be used, including thin sheet steel. However, steel is not a. preferred material. Fabrics that are freely permeable to sound and that are in themselves sound absorbing, such as wool or mineral wool elts, may be used. The use of such sound absorbing ielts, however, is not necessary, as sound, may be adequately dissipated and absorbed by an acoustical block of the type illustrated, without the assistance of materials of constructions that are themselves eective sound absorbers.

The acoustical structure of the present invenz tion may be applied to buildings in a convenient manner.

In the acoustical treatment of a room,'for example, the units may be nailed, fastened in frames, or otherwise secured to the ceiling or a wall of the room. If desired, the units may be arranged so that a sheet of material ofv perforated plane surface is on the outer or exposed face of the unit. When a given area of the ceilingv or wall is coveredwith such units, the units may abut at their 'side edges. Sound waves may pass from the edge of one unit into the spaces in an adjacent unit.

When sound strikes the perforated exposed face of the unit, it enters through theperforations.

.Because of scattering and also because of the cause the lsound to be repeatedly deected, in

partuand to pa@ through the perforations into adjacent' laterally extending spaces dened by other layers of sheet material in the composite. The passage through the periorations and laterally extending spaces and the deection oi the sound is repeated a great number of times. In

lr; fact, the sound may be caused to travel, in part,

at least, through a course oi great length, may,

greater than the wave length oi the soundin a labyrinth of spaces. During this message oi "sound in a cour that mayl be ci iniinite iength, nracticalit' eresmas. a small mount oi the sound Y may escape from the surface ci the unit. However, the disconunuity ci the perforations or communications and the fact that the laterally extendingspaces are relatively large in area ci cross section, that is, larger in cross section than the several perforationa'and, therefore, oer less resistance to the passage ci sound therethrough,

3 favor the dissipation of the sound within the unit. Also, the simulation of the sound within the unit, with repeated incidence and deection, causes the gradual ydestruition oi the sound, by

' the conversion of ,its energy into heat. J

The sound absorbing units may be'fabrlcated in vany suitable manner. l Thus. units oi the type illustrated in Figs. -S

may -be made by a method involving the process and apparatusjdescribed in U. S. Patents 1,444,-

395-6, issued on February 6, 1923, to seigle. iis-l bestos paper is made in a conventional manner.

It is then perforated, as, for4 example, by passage between coacting rollers, one of which is provided with short piercing pins and the other with ldepressions or dies which mesh with the piercing pins. vAfter the paper is perforated, a

Vportion of the paper is corrugated and crossindented, as described by Seigle. Sheets of plane surface suitably including the cross-indentations described and of corrugated surface are then composited in alternate layers. The sheets may be held together by an adhesive. Thus, an aqueous solution of sodium silicate may` be'applied to the opposite sidesof the corrugated sheets in such manner as to wet the tops of the crests andi the outside of the bottoms of the troughs. The

corrugated sheets with the streaks oi adhesive thus applied are e then adhered to alternating sheets of plane surface. This procedure is repeated until there 'is built a composite or block of the thickness desired. y

The composited block may, have various dimensions. A block may be t to 5 inches or more in thickness and oi length and breadth suited to the installation in which the block is to be used. Thus, the block may havev faces that are l x 1 feet, 2 x d feet, or of other suitablesize. Perforations that may be used have been described, although it is to be understood that many' other sizes and spacings may be used. The corrugations, likewise, may be of various widths or heights. Thus, the corrugations may be V5 inch in width, from crest to crestlv There may be 5 to 10, say d, layers each of alternating corrugated sheets having the cross-indentations described and sheets of plane surface',I per inch of thickness of the block.

The modification illustrated in idg. t may be fabricatedl by adhesively or otherwise securing together a ielted brous product comprising spacing means and made as described, for example, in U. S. Patent 1,218,679, issued March 13, 1917, to lidanville. .There may be made a ielted sheet, such as asbestos paper, comprising embedded spacing means, such as particles of corn cob, sponge, or the like. After these sheets are made and dried, they are provided with adhesive over the high spots and are composited to give a block of the thickness desired.

we products of the present invention are eec; tive m acoustical units. With units i inches thick, ofthe type illustratedV in Figs. 1 3, there has been absorbed 89% of incident 'sound oi' a frequency of 512 cycles per second.

The products are also edective in heat insulation. A typical block` oi perforated and composited asbestos sheets oi plane surface and corirrigated sheets weighs only approximately 1l pounds per cubic foot. V

The term perforation is used herein to define openings adapted to transmit incident sound.

The details that have been given are for the purpose oi' illustration and not restriction of the invention, yand many variations therefrom may be made without departing from the scope o! the invention.

What I claim is: v l. An acoustical unit comprising composited sheets provided each vwith. perfor-ations adapted to'admit incident sound and defining sound absorbing spaces extending laterally in a direction approximately parallel to the face oi the unit,

spirit and the said perforations in one layer of the said sheets being non-registering with the perforations in adjacent layers of the sheets and adapted to cause distribution of incident sound throughout the laterally extending spaces.

2. An acoustical unit comprising composited sheets provided with perforations adapted to admit incident sound and defining laterally extending spaces of relatively large area ofv cross section adapted to oier less resistance per unit of length to the passage of sound therethrough than onered by the several pertorations, and constrictions in the spaces at intervals for deecting sound.

3. A sound absorbing unit comprising a plurality of composited, non-nesting sheets of corrugated and cross indented paper provided with spaced perforations adapted to admit incident sound.

4. Sound absorbing means comprising composited, spaced relatively thin sheets provided severally with spaced openings adapted to admit incident sound and provided also with irregularities of surface extending between adjacent sheets and determining the spacing of the sheets from each other in non-contacting positions, the said perforatlons in one layer of the said sheets being largely non-registering with the perforations in adjacent layers of the sheets and the spaces defined between the sheets being adapted to absorb sound.

RAYMOND V. PARSONS. 

